This invention relates generally to motors and specifically to an electromagnetic motor with an isolated brush card assembly.
It is common to use a variety of direct current (dc) electromagnetic motors within automotive vehicles. Typical operating applications include window lift motors, windshield wiper motors, anti-lock braking system motors, et cetera. The aforementioned motors often have brushes and commutators. Traditionally, the brush riggings for these motors vary in design but in general consist of boxes to house the brushes, a spring means to apply pressure to the brushes urging them against the commutator, and electrical leads to provide a current path to the brushes. A mounting surface secures these elements as well as provides a means to secure an entire brush card assembly to a housing in such a manner as to place the brushes in a proper working relationship with the commutator.
One of the most popular conventional designs, especially for small fractional horse power dc motors, is to utilize a single piece molded brush card member formed from a high temperature resistant plastic which is electrically nonconductive. The brush card member further has a pair of brush boxes formed thereon as well as an opening for receiving a portion of an armature shaft and the commutator secured to the shaft. This type of motor and brush card construction is disclosed in U.S. Pat. Nos.: 5,006,747 entitled "Dynamoelectric Machine Brush Rigging and Method of Assembly," which issued to Steward, Sr. on Apr. 9, 1991; and 4,694,214 entitled "Brush Holder for Dynamoelectric Machines," which also issued to Steward, Sr. but on Sep. 15, 1987, both of which are owned by the present assignee and are incorporated by reference herewithin.
While the aforementioned brush card constructions are significant improvements within the art, in recent years, the sound generated by the other motor components (such as bearings and gears) has been reduced to the point that the interface between the brushes and the commutator are now considered a significant contributor to the overall motor sound level. Since the armature and the commutator rotate up to 6,000 revolutions per minute, obtrusive noise is created by the brushes rubbing against the commutator surface and by the brushes catching on grooves longitudinally present along the exterior surface of the commutator. Accordingly, any vibration which is generated by interface of the brushes and commutator is transmitted along the brush card and through the adjacent armature housing and gear housing of the motor. This creates an undesirable audible sound.
Furthermore, water must be prevented from entering the joint between the armature and gear housings. This is traditionally accomplished by insertion of a separate seal or gasket between the brush card member and the armature housing. This necessitates extra parts, tolerance stackups and assembly labor costs.
Therefore, it is desirable to have a motor with a vibrationally isolated brush card assembly that also serves to seal between an armature housing and a gear housing.